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United States Patent O ice illd Patented lidar. 3l, ld@

s 126 579 APPARATUS non THE MEASUREMENT AND CON- TROL 0F THE MODULU FILAR STRUCTURES S 0F ELASTICITY IN This invention relates to arrangements and equipment for thecontinuous measurement of the tensile modulus of elasticity (sometimes called Youngs modulus) of moving films and filamentous material herein collectively called filar structures. One capacity of the invention is to use such measurement to control means for treating synthetic fibers or films to impose desired alteration or correction of Youngs modulus of elasticity therein. More particularly, the invention in one aspect relates to improved equipment for measuring the modulus of elasticity of moving filar structures, using electromechanical techniques. When such measurements are obtained continuously from moving filar structures while these are being produced, such measurements may be used according to another aspect of the invention to control the take-up drive of the fiber or film producing apparatus and vary the' stretch imposed on the fiber or film to maintain a desired modulus of elasticity. In equipment according to this invention, whether used to control the quality of synthetic filar structures, or used simply in testing and studying the processes which occur during the mechanical deformation of such natural or synthetic structures, or used in some other fashion, this invention in a further aspect includes a novel electromechanical transducer assembly or element for transmitting or receiving longitudinal vibrations to or from a moving sample.

The three aspects of the invention may be identified herein as (A) an improved contact element for transmitting and/or receiving longitudinal mechanical vibrations in filar structures, (B) an improved arrangement for continuously measuring or testing the modulus of elasticity of successive sections of elongated filar structures,l using the improved Contact element, and (C) a technique for controlling the modulus of elasticity of moving man-made filar structures during a stage in their production, automatically governing the controlling medium by changesin the continuously measured modulus of elasticity of the structures being produced. c Thread-like and sheet-like structures are herein called filar structures and this term is intended to include not only monoiilament or multiple continuous filament fibers, but staple fiber products, such as threads made from natural cotton, wool, or spun silk. Not only this, but the term encompasses films such as vinyl, polyethylene, regenerated cellulose and the like and papers, because these sheet-like structures exhibit some of the properties of filaments and thread-like structures although they are extended in width.

In the testing of continuous fibers and i'ilms it has been established that the velocity of sound transmitted lengthwise in a given sample has a definite relation to its Youngs modulus of elasticity. However, existing methods and equipment for testing or measuring the modulus of elasticity of filar structures do not lend themselves to the continuous measurement of the modulus in rapidly moving bodies such as would be encountered during production of such filar structures. Therefore the prior systems and devices are largely limited to Vlaboratory use on short samplings of fibers and films. One object of the present invention is to provide improved apparatus for measuring the propagation velocity of longitudinal mechanical waves continuously in moving fibers, threads,

had sheets or films, and thereby measuring the modulus of elasticity of such filar structures, such apparatus being suitable for inspecting or testing continuous filaments, films and the like and useful during their production, not being limited to use under laboratory conditions or for short sample lengths.

It has also been found that during production of synthetic fibers and films a certain amount of stress imposed by drawing the material soon after it leaves the spinnerettes or lm producing apparatus will, within limits, increase the average molecular orientation lengthwise within the fiber or film and increase Youngs modulus of elasticity in the resulting product. For example, in the production of synthetic bers, known processes include the step of drawing the fiber or producing a secondary stretch to gain this desired effect. However, even when the drawing of synthetic fibers is conducted under precalculated conditions, the end product may not always be uniform because of variations in production conditions preceding the secondary stretch. These variations may produce undesirable variations in the Youngs modulus of the fiber being produced, a quality which should be kept uniform for many purposes. Another object of the present invention is therefore to provide a means for controlling the amount of stretch of synthetic fibers and films as they are being produced, this means for control being automatically governed by variations in the modulus of elasticity of the filar structure itself, correcting or adjusting the stretch to produce an end product of a desired uniform or variable modulus.

An object related to the above noted measuring and controlling aspects is to provide an improved contact element for transmitting and receiving longitudinal inechanical vibrations in moving filar structures, such an element being useful in laboratory testing of such structures, in production measurement of the modulus of elasticity of fibers and films in production, in continuous control of the modulus of elasticity of synthetic fibers or lms in production, and in other applications.

Other objects, advantages and further details of that which is believed to be novel and included in this invention Will be clear from the following description and claims, taken with the accompanying drawing in which is illustrated an example of apparatus embodying the present invention and incorporating the improvements outlined above.

`In the drawings:

FIG. l is a diagram or simplified layout in side view indicating a preferred arrangement of equipment for continuously measuring the modulus of elasticity in moving synthetic filar structures, and for controlling the modulus;

FIG. 2 is a perspective View of a transmitting-receiving unit or element of the invention, useful as a transducer in the measuring and controlling aspects of the invention;

FIG. 3 is a side elevational view of the transducer assembly of FIG. 2, parts being broken away for clarity in illustration;

FIG. 4 is a vertical sectional view on the line 4 4 of FIG. 3 showing how various parts may be supported and secured, and

FIG. 5 is a vertical sectional view on the line 5 5 of FIG. 3 showing other details for securing and supporting the parts.

In carrying out the objects of the invention according to one embodiment thereof a constant rate driving drum 11 receives the filament or filaments of a fiber F from the spinnerettes of a synthetic fiber producing machine soon after the fiber is formed in the machine. The fiber F passes over the constant rate driving drum 1l, and is looped once or twice around a cylindrical stretch or snubbing pin 13, of glazed ceramic material, and is then passed over a tension drum l5, similar to the drum il but normally driven at a constant precalculated rate substantially above the speed of the constant rate drum 11, The drums 11 and `15 are usually made exactly one foot in circumference so that the rate of drive of the filament in revolutions per second is equal to the number of feet per second at which the fiber is driven opposite each drum. The stretch pin 13 is fixed, that is, nonrotatable, and may or may not be heated. This pin serves as an anchor for the fiber moving thereover and the filament is drawn between this pin and the tension drum because of the differential Iin driving speeds between the drums 11 and 15. The drawing of the filament is assumed to take place in the last quadrant of the last turn around the pin before it leaves the pin. Such pins are known in apparatus for producing synthetic fibers, yand they are usually not smaller than of an inch in diameter `and not larger than of an inch in diameter.

When the drawn filament leaves the tension drum 15 it may pass to other equipment for further processing of the fiber or to a take-off reel or other storage arrangef ment for the completed fiber. The differential speed driven drums and the stretch pin above described may be considered as known conventional equipment in the production `of synthetic fibers. The present invention is concerned-in its controlling aspect-with continuously or periodically measuring the modulus of elasticity of the fibers and with using these measurements automatically to adjust or correct the amount of secondary stretch imposed on the fibers while they are being produced. In this way the modulus of elasticity of the fibers can be controlled within much closer limits than heretofore.

Measurement of the modulus of elasticity of the fiber is accomplished through a transmitter 17 and a pick-up or receiver 19, which, for manufacturing economy may be substantially identical, or they may be somewhat different in nature. In the example shown, each transducer includes a vibratory conversion unit or element 21 indicated here as a Rochelle salt crystal sandwich-like assembly. Electrical leads 23 may be connected to the crystal.

Other types or forms of electromechanical transducer elements might be used, such as magnetic reed-like vibrators, polycrystalline ceramic elements and other piezoelectric materials. The transmitter and receiver are each mounted at a xed location alongside the path of movement of the test sample.

The transmitting transducer 17 is intended to impose longitudinal mechanical waves or pulses on the moving ber, while the pick-up or receiving transducer 19 is intended to detect 4these waves or pulses when they have passed along the test length of the fiber between the two transducer locations. 1n the transducer units shown as an example there is a supporting shell or housing 25 of insulating material with an internal cavity 27 in which the crystal 21 is received and protected, three of the corners of the crystal being securely held in place against movement as by projections 29 in the cavity, which bear against -sides of the crystal at the corners thereof. The fourth corner of the crystal is left free from support so that as vibration is produced in the crystal or induced by external action the free corner is the only one left to move and the vibration will be concentrated on that corner.

Important in the element aspect of the invention is the means whereby mechanical vibrations may be transmitted from the crystal or other vibratory transducer element to the filament or from the filament to the transducer element. lf there were no relative motion between the fiber sample and .the transducers, and the transducers contacted the fiber directly, the interface contact between transducer and test specimen would be stationary and the forces developed by the transducer in transmission and by the sample in reception would be provided by the static friction between specimen and transducer. However, motion of the sample with respect to the transducers would result in the loss of good interface Contact and the amount of motion imparted to the test specimen for a given amount of motion of the transducers would be reduced because of the substitution of moving friction for the static friction. Moving friction also would add random vibrations or noise.

According to this invention, a rotatable circular contact in the form of a tiny pulley, roller or wheel 31 is mounted on the transducer to rotate in the plane of vibratory motion of the transducer, which is the same plane along ywhich the fibers move. Due to the rotational inertia of the pulley, the vibratory amplitude imparted to the sample is comparable to that which would be imparted with a `static friction contact. As shown here, each circular contact 3'1 is supported on a spindle 33, the ends of which are mounted in a freely rotatable manner between opposed arms 35 of a mounting bracket which is firmly secured to the vibratory corner of the transducer crystal. The spindles may be mounted in jeweled bearings for reasons of wear resistance, low friction and low noise, and the bracket may be fastened to the transducer by means of cementing or in some suitable fashion which will anchor the bracket securely without damaging the vibratory element.

The rotatable circular contact element or pulley 31 as here shown is provided with a V-groove in its periphery, for the purpose of insuring guidance of the moving filament or thread thereon. Other forms of grooves might be used if desired when applied against a filament, but when the transducer element is used against a film, web, or sheet, the circumference of the circular contact element is preferably cylindrical and not grooved because when the width of the test sample is greater than the pulley it requires no guidance on this rotary contact element.

With an arrangement such as described, the pulley or wheel is free to rotate at a peripheral velocity equal to the forward transport velocity of the movnig test specimen, with only the friction forces between spindle and bearing to retard such motion. The transmission of the vibratory motion of the transducer to the test specimen is possible because of the rotational inertia of the pulley, provided that the vibration frequency of the transducer and the rotational inertia of the pulley are both high enough to prevent a significant amount of loss of the lateral motion of the transducer by a signal-cancelling rotational movement of the pulley. Therefore, as the transducer vibrates, its motion is transmitted to the test specimen through the pulley, and conversely at the pickup the longitudinal vibratory motion of the fiber is transmitted through the pulley to the receiving transducer.

Although in the form of apparatus shown diagrammatically `in FIG. l the propagation velocity of longitudinal vibratory waves in the moving fiber is measured between the stretch pin and the tension drum 15, much the same effect may be obtained by locating the testing or measuring section elsewhere on the moving fiber before it is stretched. In any case, the measuring and controlling equipment may include an oscillator 39 sending an electrical signal both through the transmitting transducer 17 and to a control element, shown here as a phase shifter 41, leading to one input of a phase detector 43. The other input to the phase detector is connected to the receiving transducer 19 through suitable filters and amplifiers 45 and the transmitter and receiver signals are thereby compared. Any resulting error signal is sent from the phase detector to suitable instrumentation for varying the speed of the tension drum y15.

in the exemplary arrangement, the phase shifter is set for `a. desired modulus of elasticity at a given spacing of the transducers or the transducer spacing is set for a given phase shifter value consistent with a desired modulus. The phase detector 43 will compare the predetermined oscillator signal coming through phase shifter `41 with the signal transmitted through the sample by receiver 19 through the filter and amplifier 45 and will produce an error signal if the two inputs do not match. The error signal is then passed to a servo amplifier 47 which is used to supply power to operate a rotational speed controlling device 49, which will control the rotational rate of the drum 15. The rate controller 49 may be in the lform of a ball and disc drive in which the ball position is automatically changed in direction and magnitude as necessary to maintain a minimum error signal, or it may consist of any one of a number of other known variable drive arrangements in which some element of the drive is controlled in such a way Ias to produce a variable corrective rotational speed.

Although the system shown in FIG. 1 and described above uses continuous wave techniques requiring an electrical oscillator to produce the signal, pulse techniques may be used inste-ad, in which case some sort of suitable electrical pulse generating device may be used instead of the oscillator, with corresponding pulse delay comparators, time differential detectors, and associated equipment, leading to the controller 49 for varying the rotational rate of the tension drum. The transducer with its rotational circular contact is useful in a pulse type system as well as in the continuous wave system. In both types of system, without the pulleys, the signals received using simply a fixed wire saddle lor direct contact on the end of the transducer elements may be far below the noise level v produced by the moving filament, Whereas with pulleys a useful signal to noise ratio can be obtained.

That section of the equipment shown and described may be used from drum 11 up to `and ending with the servo amplifier 47 alone, and /without feed-back to the rotational r-ate control. In that case it becomes a continuous measuring system, according to the measuring aspect of the invention, and the signals from the amplifier go to suitable instruments which indicate and/or record variations in the modulus of elasticity of the moving ilar structure. A useful laboratory test set-up may be made along these lines, either by moving the liber between rollers or drums :similar to the drums 11 and 15 and across iixedly spaced transducers like 17 and 19; or by holding the ends of a fiber or ilm sample fixed and moving xedly spaced transducer stations simultaneously along the sarnple. The laboratory equipment would not need to 1nclude a stretch pin, but any desired tension load could be applied in known fashion to one end or iother of the fiber or the film sample.

It should be evident that the transducer assembly by 1tself, with its rolling contact element, is useful in the production control of Youngs modulus in synthetic fibers and lilms, in the measuring or testing of the modulus of elasticity in moving iilar structures for production records or laboratory analysis, or in the effective transmission or reception of longitudinal mechanical vibrations along a moving iilar structure for any other purpose.

Although vibrations of the transducer in the sonic and ultra-sonic range have been used successfully with apparatus according to the invention, any mechanical longitudinal oscillation is regarded as useful in carrying out the inventive concept involved, considering such factors as the space available, the rate of resolution, Wave length of the oscillation, etc. When the iilar structure involved is a continuous filament or film type, the modulus of elasticity of the structure indicates the degree of molecular orientation in the liber or lm composing the structure, and is related to the stiffness of the product. When the lar structure is of the staple iiber or paper sheet type, the modulus of elasticity of the structure indicates individual fiber orientation, which is related to the degree of twist in threads and to tear strength in a particular direction in paper-like structures.

As will be evident from the foregoing, certain aspects of this invention are not limited to the particular details given above, and it is contemplated that various and other modifications and applications of the invention will occur to those skilled in the art. It is therefore intended that the appended claims shall cover such modications and applications as do not depart from the true spirit and scope of the invention.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:

l. In apparatus for producing a synthetic elongated iilar structure which includes means for drawing such structure while it is in longitudinal transporting motion, that improvement comprising a transmitter element introducing mechanical longitudinal vibratory signals onto the moving structure,

a receiver element sensing said signals from said moving structure at a fixedly spaced distance therealong from said transmitter,

said transmitter and receiver elements each including a rotatable circular contact journaled about its center on the element and adapted to bear against said ilar structure for rotative movement in the direction of the longitudinal vibratory signals on the structure and of longitudinal transporting movement of said structure,

means for comparing said transmitted and received signals, and

means varying the action of said means for drawing said structure, said means varying in response to differences between said compared transmitted and received signals,

whereby said means for drawing the iilar structure is governed by the signals on the moving structure between said transmitter and said receiver.

2. Apparatus for controlling the modulus of elasticity of a synthetic liber filament by stretching the filament comprising a constant rate driving drum,

a variable rate tension drum,

a stretch pin between said drums,

said liber lament passing from said driving drum,

around said stretch pin and to said tension drum,

a transmitter introducing longitudinal vibratory signals to said ber between said stretch pin and said tension drum,

a receiver sensing said signals from said liber between said transmitter and said tension drum,

said transmitter and receiver each carrying a freely rotatable circular contact element thereon journaled about a central axis normal to the extent of said cer lament and to the plane of the longitudinal vibratory signals on said filament and adapted to bear rotatively against said liber filament,

means for measuring the modulus of elasticity of said ber by comparing the transmitted and received signals,

a variable speed drive for said tension drum,

means controlled by said means for measuring said modulus for regulating the speed of said variable drive,

to produce a stretching of the fiber such that a preselected modulus of elasticity is obtained in the liber,

whereby the liber filament is stretched by amounts governed by the modulus of elasticity measured by transmission of said longitudinal vibratory signals along the liber between said transmitter and said receiver, to produce a fiber filament having said preselected modulus.

3. In apparatus for measuring the modulus of elasticity of a ilar structure along a length of such structure in relative longitudinal motion with respect to a pair of spaced testing stations, comprising a longitudinal vibration transmitting transducer including a contact element at one of said testing stations, a longitudinal vibration receiving transducer including a contact element at the other of said testing stations, means imposing a vibratory signal through said transmitting transducer and its contact element to said structure longitudinally thereof, means sensing said longitudinally imposed signal from said structure at said receiving transducer through its contact element and means comparing the longitudinally transmitted signal with the received signal whereby the longitudinal acoustic velocity of the signal in the structure is determined and indicates the modulus of elasticity of the length of lar structure then in the space between the testing stations,

that improvement in which each of said contact elements comprises a rotatable circular member mounted on each said transducer, journaled about a central axis and adapted to extend between said transducer and said structure with its periphery bearing against said filar structure,

the journal axis of each said circular contact member being normal to the direction of relative longitudinal motion between said structure and said testing stations and normal to the direction of the longitudinal vibrations of said transducers.

4. In apparatus for measuring the modulus of elasticity of a lar structure along a length of such structure moving between a pair of spaced testing stations, comprising a vibration transmitting transducer at one of said testing stations with a contact element oscillating lengthwise of said ilar structure, a vibration receiving transducer at the other of said testing stations with a contact element oscillatable lengthwise of said ilar structure, means applying a vibratory signal through said transmitting transducer and its contact element longitudinally to said moving structure, means sensing said longitudinal vibratory signal from said moving lar structure at said receiving transducer through its contact element and means comparing the transmitted longitudinal vibratory signal with a vibratory signal as received, whereby the longitudinal acoustic velocity of the signal in the structure is determined and indicates the modulus of elasticity of the structure moving between the testing starions,

that improvement wherein each said contact element comprises a circular contact member rotatably mounted on each said transducer with its circumference bearing against said lar structure, the rotation of each contact member being lengthwise of said structure in the direction of its movement between said testing stations and in the direction of lengthwise vibration of said transducers. 5. An element for transmitting and receiving longitudinal mechanical vibratory signals on a longitudinally 10 extending iilar structure, comprising a vibratory transducer oscillating in the direction of longitudinal extent of said lar structure,

a rotatable circular contact on said transducer journaled about a central axis and adapted to bear at its periphery against said lar structure,

the journal axis of said contact being normal to the direction of vibration of said transducer so that said contact is rotatable with respect to said transducer in the direction of longitudinal extent of the iilar structure and in the direction of oscillation of said transducer.

References Cited in the le of this patent UNITED STATES PATENTS Rich Apr. 26, 1955 Haw Mar. 29, 1960 OTHER REFERENCES 

1. IN APPARATUS FOR PRODUCING A SYNTHETIC ELONGATED FILAR STRUCTURE WHICH INCLUDES MEANS FOR DRAWING SUCH STRUCTURE WHILE IT IS IN LONGITUDINAL TRANSPORTING MOTION, THAT IMPROVEMENT COMPRISING A TRANSMITTER ELEMENT INTRODUCING MECHANICAL LONGITUDINAL VIBRATORY SIGNALS ONTO THE MOVING STRUCTURE, A RECEIVER ELEMENT SENSING SAID SIGNALS FROM SAID MOVING STRUCTURE AT A FIXEDLY SPACED DISTANCE THEREALONG FROM SAID TRANSMITTER, SAID TRANSMITTER AND RECEIVER ELEMENTS EACH INCLUDING A ROTATABLE CIRCULAR CONTACT JOURNALED ABOUT ITS CENTER ON THE ELEMENT AND ADAPTED TO BEAR AGAINST SAID FILAR STRUCTURE OF ROTATIVE MOVEMENT IN THE DIRECTION OF THE LONGITUDINAL VIBRATORY SIGNALS ON THE STRUCTURE AND OF LONGITUDINAL TRANSPORTING MOVEMENT OF SAID STRUCTURE, MEANS FOR COMPARING SAID TRANSMITTED AND RECEIVED SIGNALS, AND MEANS VARYING THE ACTION OF SAID MEANS FOR DRAWING SAID STRUCTURE, SAID MEANS VARYING IN RESPONSE TO DIFFERENCES BETWEEN SAID COMPARED TRANSMITTED AND RECEIVED SIGNALS, WHEREBY SAID MEANS FOR DRAWING THE FILAR STRUCTURE IS GOVERNED BY THE SIGNALS ON THE MOVING STRUCTURE BETWEEN SAID TRANSMITTER AND SAID RECEIVER. 